The world of literature and media are infected with the threat of zombies. In general, zombies have lost their humanity and are out for blood. If you get in contact with them either by saliva or by blood you will get infected and eventually lose your humanity and try to kill and devour your loved ones. However, you will come to see that there are two types of zombies. Both are similar in that they have lost their humanity and all they want to do is snack on a brain, but both are different in ways involving the infection and virus itself, the traits of the two types of zombies, and the ways to kill them. This discussion will compare and contrast the two types of zombies.
The first type of zombies are those in The Walking Dead, also similar to the zombies in Dawn of the Dead and Shaun of the Dead. Typically, the zombie virus that is associated with The Walking Dead and other novels and media depicts the general, slow-paced, and undead zombie can take maybe a week or more to make a single city, much less an entire state, get infected. These zombies usually take hours or even days to actually get turned into a zombie. The infection is a process; first they're relieved that they just survived from getting a chunk of their arm being bitten off by a zombie, then they usually lose their strength and energy, becoming more tired and probably more irritable and giving into their anger issues, and finally they become one of the undead by either succumbing to their injuries or getting shot by a friend who is just trying to save them from a life of being a zombie. Since the infection can take a while to spread, if you happen to get bit in the leg and you are aware of how the infection works, then you can simply cut off your leg and survive from being a zombie.
These zombies are slow, it can take them a while to go a mile, their slow-motion movements give you enough time to run and hide, say maybe to a prison. They do love to travel in herds, so if you happen to not be able to outrun a slow zombie, then lights out. These zombies are undead, it doesn't matter if the infected is already dead, they will turn into a zombie, even if its just a torso trying to crawl to its next meal or an armless zombie with their jaw and teeth removed and being used as attack dogs. Since these zombies are undead, the only way to kill them is by shooting them in the brain.
The second, and probably most deadly, zombies are those in World War Z, similar to the zombies in Zombieland and 28 Days Later (and also The Crazies, but there's a debate whether the infected in The Crazies were actual zombies). These zombies get infected within seconds, they get bit and they don't have time to cut off the infected limb because they're too busy convulsing on the ground and getting turned into a mindless cannibal. Since the infection takes mere seconds, the infection of an entire city would only take maybe a few hours, depending on the size.
These zombies, unlike their slow counterparts, are still technically alive, but they are just transformed radically (mentally and physically) by a viral infection. They feel no pain and they don't get thirsty or hungry, but since they are technically alive they can die from hydration or starvation, they still depend on all of their organ systems, so they can be killed through blood loss, asphyxiation, and even poisoning. These fast zombies are more of a threat than slow zombies, they are clever and can easily build a ladder of zombies to climb up a hundred foot wall, and unless you’re a track star, you're not going to be able to outrun them, but they are weaker in the sense that if you shoot them they will eventually bleed out and die.
In conclusion, any type of zombie would suck, you will have to make sure that you're all stocked up on ammunition. However, even though these two type of zombies are drastically different, they share similarities; they both crave human flesh and they couldn't care less if you're their significant other or their favorite aunt or even their only child, they only want human flesh and they will do anything to get what they want. Even though the fast zombies are still alive, they are harder to kill compared to a normal person who's not infected with a deadly virus, and although they don't need to be killed by getting shot in the brain, it's not a bad idea.